1. Field of the Invention
The present invention relates to an aquaculture system for raising either fresh water fish, or salt water fish, in which growing fish of about the same size are kept together in each growth stage, and as they are moved from one growth stage to the next growth stage.
2. The Prior Art
Various kinds of shrimp-farming and/or fish-farming processes and apparatus have been proposed in the prior art; and these are described in the following documents.
______________________________________ U.S. Pat. No. Patentee Date ______________________________________ 3,473,509 Miyamura October 1969 3,765,372 Moe, et al. October 1973 4,052,960 Birkbeck, et al. October 1977 4,213,421 Droese, et al. July 1980 4,738,220 Ewald April 1988 ______________________________________
A method for the selective breeding of trout is described in Soviet Union Published Application No. SU 1110427A, published Aug. 30, 1984.
Cannibalism has been noted in two working multi-component fresh culture systems by Van Gorder. In the Pineville site losses of striped bass where recorded to be over 80%. The Kutztown facility recorded losses of up to 65%. Both systems were intensive systems without graders; and in the Pineville system low feed rates of food were also noted which accounted for the higher loss rate over the Kutztown site.
The "Performance Capacity of Organisms, Stress and Water Quality" was a paper presented by Schreck at Aquaculture '89. In this paper were reported the results of tests on the energy drain and reduced immune response for Salmonid species during a 30 second dip netting test in a high density situation. It was noted that there was a 22% death rate due to the netting procedure.
The "Physiology Research to Net Stress in Striped Bass; Effect of Acclimation Temperature" was a paper presented by Davis and Parker at Aquaculture '89. This paper reported that up to 66% death occurred and the highest rate of loss occurred when a netting procedure under intensive circumstances occurred. Increased disease, depressed growth also occurred. The effects of the stress was evident for a period up to 48 hours after the netting. Also death did not occur instantly and was noticed during the 48 hour period after netting.
In the "Current Design Of The Fresh Culture System" by Van Gorder, netting stresses accounted for up to 20% death of striped bass when moved by net from one body of water to another. Fewer losses where noted when water and fish where moved in a bucket type container.
It is noted by Sticknet in "Culture of Nonsalmonid Freshwater Fishes" that striped bass are more excitable than other commonly cultured species and that fatal shock may occur during handling of the fish.
All of these prior art proposed aquaculture systems suffer from the following disadvantages. Fish of different species may be placed together in the same tank, or fish of the same species but of different sizes can be placed together in the same tank. This results in the larger, of a predatory fish, eating the smaller fish, thereby greatly reducing the fully grown fish available to be harvested from the fish farming system.
In the prior art systems, the fish are physically moved by net from one growing tank to another in a batch operation. This can readily result in a greatly increased incidence of disease or death for the fish, due to greatly increased stress caused to the fish and due to the removal of the fish secretion mucous layer, or "slime layer". This mucous layer covers the skin of the fish to protect it from disease.
In the prior art systems, whenever younger smaller fish are introduced into the system, there is a likelihood that if any are sickly that they may infect other healthier fish, because there is no quarantine chamber for newly arrived fish.